1. Field of the Invention
This invention relates to the use of thickening agents in acetylene vessel filler compositions.
2. Description of the Prior Art
In conventional practice, acetylene gas is commonly stored in the form of a dissolved acetylene gas solution, as for example in acetone solvent, in a vessel containing a cured, hardened porous mass of calcium silicate. Typically, the porous mass of calcium silicate filler material is formed from a mixture of crystalline sand or silica and quicklime (calcium oxide) dispersed in water to form a aqueous slurry. The aqueous slurry composition is then reacted at high temperature and saturated steam pressure to form the cured, hardened porous mass of calcium silicate.
In prior art practice, a variety of thickening agents have been employed in the preparation of the calcium silicate porous mass. Introduced into the aqueous slurry composition, these thickening agents function to prevent settling of the slurry composition, and thereby prevent an excessive amount of water from separating from the slurry composition which in turn would otherwise lead to non-uniformity in density of the product composition and to deleterious excessive clearance between the cured, hardened porous mass of calcium silicate and the walls of the acetylene vessel in which the filler is employed.
Although a large number of inorganic and organic thickening agents are known in the art of making porous masses of calcium silicate for such uses as acetylene vessel fillers and insulation media, all such thickening agents have associated shortcomings. Examples of such thickening agents include fresh aluminum, magnesium hydroxides, aluminum sulfate, sodium carbonate with a trace of sulfate, sodium aluminate, basic magnesium carbonate, phosphoric acid or a phosphate material, boric acid or a borate material, certain clays, sugar and water soluble ethyl hydroxyethyl cellulose. Most of these materials are relatively expensive. In addition, some of the afore-mentioned thickening agents, as for example, small amounts of aluminum compounds, can exhibit the growth of xonotlite crystalline phase, and larger amounts of aluminum compounds can inhibit the growth of both xonotlite and tobermorite crystalline phases in the product calcium silicate filler mass. High fractions of xonotlite and/or tobermorite crystalline phases in the calcium silicate product are preferred, since these crystalline phases provide a higher strength filler than the non-crystalline, amorphous forms of calcium silicate otherwise produced. Finally, with the addition of organic thickening agents such as sugar and ethyl hydroxyethyl cellulose to the aqueous slurry composition which is cured to form the porous calcium silicate product, a significant reduction in filler strength is generally observed.
Accordingly, it is an object of the present invention to provide a relatively inexpensive thickening agent for the aqueous slurry composition which is cured to form the porous mass of calcium silicate.
It is another object of the invention to provide such a thickening agent which is in no way deterimental to the manufacturing process of the calcium silicate product or the physical properties thereof. Other objects and advantages will be apparent from the ensuing disclosure and appended claims.